When an object moves with respect to stationary references such as a ground plane, fixed points, lines or reference surfaces, knowledge of the object's absolute position with respect to these references can be used to derive a variety of its parameters of motion as well as its pose and absolute position with respect to any of these stationary references. Over time, many useful coordinate systems and methods have been developed to track the pose and absolute position of objects and to parameterize their equations of motion. For a theoretical background the reader is referred to textbooks on classical mechanics such as Goldstein et al., Classical Mechanics, 3rd Edition, Addison Wesley 2002.
In one field it is important to know the absolute position of a tip of an elongate object while the tip is in contact with a plane surface. Now, various types of elongate objects can benefit from knowledge of their pose, and more precisely the absolute position of their tip while in contact with a plane surface. These objects include walking canes when in touch with the ground, pointers when in touch with a display, a screen or a projection surface, robotic arms when in touch with a plane surface, writing devices when in touch with a writing surface, and styluses when in touch with an input screen or pad.
The need to determine the absolute position of the tip or nib of an input device shaped as elongate objects is related to data processing. In particular, the absolute position of the tip has to be known in order to analyze the information written or traced by the user. The art of writing and drawing is ancient and rich in traditions. Over the ages various types of implements have been used for writing down words as well as drawing, sketching, marking and painting.
Most of these implements have a generally elongate shape, an essentially round cross-section and they are terminated at one end by a writing nib or tip. They are typically designed to be hand-held and operated by the user's preferred hand (e.g., by the right hand for right-handed persons). More specifically, the user moves the implement across a writing or jotting surface such that the writing nib leaves a visible trace marking its motion on the surface. The marking can be produced by a material deposited from the nib, e.g., through abrasion of the marking material (such as charcoal or graphite in the case of a pencil) or by direct wetting of the surface by an ink (as in the case of the pen). The marking can also include any other physical trace left on the surface.
The most widely used writing and drawing implements include pens and pencils while the most convenient jotting surfaces include sheets of paper of various sizes and other generally planar objects capable of being marked. In fact, despite the tremendous advances in sciences and engineering, pen and paper remain among the simplest and most intuitive devices for writing, drawing, marking and sketching, even in the electronic age.
The challenge of communicating with electronic devices is in the very input interface to the electronic device. For example, computers take advantage of input devices such as keyboards, buttons, pointer devices, mice and various other types of apparatus that encode motion and convert it to data that the computer can process. Unfortunately, none of these devices are as user-friendly and accepted as pen and paper.
This input interface problem has been recognized in the prior art and a variety of solutions have been proposed. Most of these solutions attempt to derive electronic, i.e., digital data from the motions of a pen on paper or some other writing surface, e.g., a writing tablet. Of these prior art teachings, the following references are of note:
U.S. Pat. Nos:
4,471,1624,896,5435,103,4865,215,3975,226,0915,294,7925,333,2095,434,3715,484,9665,517,5795,548,0925,577,1355,581,2765,587,5585,587,5605,652,4125,661,5065,717,1685,737,7405,750,9395,774,6025,781,6615,902,9685,939,7025,959,6175,960,1245,977,9586,031,9366,044,1656,050,4906,081,2616,100,8776,104,3876,104,3886,108,4446,111,5656,124,8476,130,6666,147,6816,153,8366,177,9276,181,3296,184,8736,188,3926,213,3986,243,5036,262,7196,292,1776,330,3596,334,0036,335,7236,335,7246,335,7276,348,9146,396,4816,414,6736,421,0426,422,7756,424,3406,429,8566,437,3146,456,7496,492,9816,498,604
U.S. Published Applications:
2002-00010292002-00280172002-01181812002-2002-014865501588482002-0163511
European Patent Specifications:
0,649,549 B1
International Patent Applications:
WO 02/017222 A2WO 02/058029WO 02/064380 WO 02/069247A2A1A1WO 02/084634 A1
Although the above-referenced teachings provide a number of approaches they are cumbersome to the user. Many of these approaches provide the user with pens that are difficult to handle, impose special writing and/or monitoring conditions and/or they require cumbersome auxiliary systems and devices to track and digitize the information written on the writing surface. Thus, the problem of a user-friendly input interface based on a writing implement has not been solved.